The
file format is based on Sun's Basic Security Module (BSM) file format, a
token-based record stream to represent system audit data.
This file format is both flexible and extensible, able to describe a broad
range of data types, and easily extended to describe new data types in a
moderately backward and forward compatible way.
BSM token streams typically begin and end with a
``file''
token, which provides time stamp and file name information for the stream;
when processing a BSM token stream from a stream as opposed to a single file
source, file tokens may be seen at any point between ordinary records
identifying when particular parts of the stream begin and end.
All other tokens will appear in the context of a complete BSM audit record,
which begins with a
``header''
token, and ends with a
``trailer''
token, which describe the audit record.
Between these two tokens will appear a variety of data tokens, such as
process information, file path names, IPC object information, MAC labels,
socket information, and so on.
The BSM file format defines specific token orders for each record event type;
however, some variation may occur depending on the operating system in use,
what system options, such as mandatory access control, are present.
This manual page documents the common token types and their binary format, and
is intended for reference purposes only.
It is recommended that application programmers use the
libbsm(3)
interface to read and write tokens, rather than parsing or constructing
records by hand.
File Token
The
``file''
token is used at the beginning and end of an audit log file to indicate
when the audit log begins and ends.
It includes a pathname so that, if concatenated together, original file
boundaries are still observable, and gaps in the audit log can be identified.
A
``file''
token can be created using
au_to_file3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Seconds4 bytesFile time stamp"
"Microseconds4 bytesFile time stamp"
"File name lengh2 bytesFile name of audit trail"
"File pathnameN bytes + 1 NULFile name of audit trail"
Header Token
The
``header''
token is used to mark the beginning of a complete audit record, and includes
the length of the total record in bytes, a version number for the record
layout, the event type and subtype, and the time at which the event occurred.
A 32-bit
``header''
token can be created using
au_to_header323;
a 64-bit
``header''
token can be created using
au_to_header643.
FieldBytesDescription
"Token ID1 byteToken ID"
"Record Byte Count4 bytesNumber of bytes in record"
"Version Number2 bytesRecord version number"
"Event Type2 bytesEvent type"
"Event Modifier2 bytesEvent sub-type"
"Seconds4/8 bytesRecord time stamp (32/64-bits)"
"Nanoseconds4/8 bytesRecord time stamp (32/64-bits)"
Expanded Header Token
The
``expanded header''
token is an expanded version of the
``header''
token, with the addition of a machine IPv4 or IPv6 address.
A 32-bit extended
``header''
token can be created using
au_to_header32_ex3;
a 64-bit extended
``header''
token can be created using
au_to_header64_ex3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Record Byte Count4 bytesNumber of bytes in record"
"Version Number2 bytesRecord version number"
"Event Type2 bytesEvent type"
"Event Modifier2 bytesEvent sub-type"
"Address Type/Length1 byteHost address type and length"
"Machine Address4/16 bytesIPv4 or IPv6 address"
"Seconds4/8 bytesRecord time stamp (32/64-bits)"
"Nanoseconds4/8 bytesRecord time stamp (32/64-bits)"
Trailer Token
The
``trailer''
terminates a BSM audit record, and contains a magic number,
TRAILER_PAD_MAGIC
and length that can be used to validate that the record was read properly.
A
``trailer''
token can be created using
au_to_trailer3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Trailer Magic2 bytesTrailer magic number"
"Record Byte Count4 bytesNumber of bytes in record"
Arbitrary Data Token
The
``arbitrary data''
token contains a byte stream of opaque (untyped) data.
The size of the data is calculated as the size of each unit of data
multipled by the number of units of data.
A
``How to print''
field is present to specify how to print the data, but interpretation of
that field is not currently defined.
An
``arbitrary data''
token can be created using
au_to_data3.
FieldBytesDescription
"Token ID1 byteToken ID"
"How to Print1 byteUser-defined printing information"
"Basic Unit1 byteSize of a unit in bytes"
"Unit Count1 byteNumber of units of data present"
"Data ItemsVariableUser data"
in_addr Token
The
``in_addr''
token holds a network byte order IPv4 or IPv6 address.
An
``in_addr''
token can be created using
au_to_in_addr3
for an IPv4 address, or
au_to_in_addr_ex3
for an IPv6 address.
See the
Sx BUGS
section for information on the storage of this token.
FieldBytesDescription
"Token ID1 byteToken ID"
"IP Address Type1 byteType of address"
"IP Address4/16 bytesIPv4 or IPv6 address"
Expanded in_addr Token
The
``expanded in_addr''
token ...
See the
Sx BUGS
section for information on the storage of this token.
FieldBytesDescription
"Token ID1 byteToken ID"
XXXX
ip Token
The
``ip''
token contains an IP packet header in network byte order.
An
``ip''
token can be created using
au_to_ip3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Version and IHL1 byteVersion and IP header length"
"Type of Service1 byteIP TOS field"
"Length2 bytesIP packet length in network byte order"
"ID2 bytesIP header ID for reassembly"
"Offset2 bytesIP fragment offset and flags, network byte order"
The
``iport''
token stores an IP port number in network byte order.
An
``iport''
token can be created using
au_to_iport3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Port Number2 bytesPort number in network byte order"
Path Token
The
``path''
token contains a pathname.
A
``path''
token can be created using
au_to_path3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Path Length2 bytesLength of path in bytes"
"PathN bytes + 1 NULPath name"
path_attr Token
The
``path_attr''
token contains a set of NUL-terminated path names.
The
libbsm(3)
API cannot currently create a
``path_attr''
token.
FieldBytesDescription
"Token ID1 byteToken ID"
"Count2 bytesNumber of NUL-terminated string(s) in token"
"PathVariablecount NUL-terminated string(s)"
Process Token
The
``process''
token contains a description of the security properties of a process
involved as the target of an auditable event, such as the destination for
signal delivery.
It should not be confused with the
``subject''
token, which describes the subject performing an auditable event.
This includes both the traditional
UNIX
security properties, such as user IDs and group IDs, but also audit
information such as the audit user ID and session.
A
``process''
token can be created using
au_to_process323
or
au_to_process643.
FieldBytesDescription
"Token ID1 byteToken ID"
"Audit ID4 bytesAudit user ID"
"Effective User ID4 bytesEffective user ID"
"Effective Group ID4 bytesEffective group ID"
"Real User ID4 bytesReal user ID"
"Real Group ID4 bytesReal group ID"
"Process ID4 bytesProcess ID"
"Session ID4 bytesAudit session ID"
"Terminal Port ID4/8 bytesTerminal port ID (32/64-bits)"
"Terminal Machine Address4 bytesIP address of machine"
Expanded Process Token
The
``expanded process''
token contains the contents of the
``process''
token, with the addition of a machine address type and variable length
address storage capable of containing IPv6 addresses.
An
``expanded process''
token can be created using
au_to_process32_ex3
or
au_to_process64_ex3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Audit ID4 bytesAudit user ID"
"Effective User ID4 bytesEffective user ID"
"Effective Group ID4 bytesEffective group ID"
"Real User ID4 bytesReal user ID"
"Real Group ID4 bytesReal group ID"
"Process ID4 bytesProcess ID"
"Session ID4 bytesAudit session ID"
"Terminal Port ID4/8 bytesTerminal port ID (32/64-bits)"
"Terminal Address Type/Length1 byteLength of machine address"
"Terminal Machine Address4 bytesIPv4 or IPv6 address of machine"
Return Token
The
``return''
token contains a system call or library function return condition, including
return value and error number associated with the global variable
Er errno .
A
``return''
token can be created using
au_to_return323
or
au_to_return643.
FieldBytesDescription
"Token ID1 byteToken ID"
"Error Number1 byteErrno value, or 0 if undefined"
"Return Value4/8 bytesReturn value (32/64-bits)"
Subject Token
The
``subject''
token contains information on the subject performing the operation described
by an audit record, and includes similar information to that found in the
``process''
and
``expanded process''
tokens.
However, those tokens are used where the process being described is the
target of the operation, not the authorizing party.
A
``subject''
token can be created using
au_to_subject323
and
au_to_subject643.
FieldBytesDescription
"Token ID1 byteToken ID"
"Audit ID4 bytesAudit user ID"
"Effective User ID4 bytesEffective user ID"
"Effective Group ID4 bytesEffective group ID"
"Real User ID4 bytesReal user ID"
"Real Group ID4 bytesReal group ID"
"Process ID4 bytesProcess ID"
"Session ID4 bytesAudit session ID"
"Terminal Port ID4/8 bytesTerminal port ID (32/64-bits)"
"Terminal Machine Address4 bytesIP address of machine"
Expanded Subject Token
The
``expanded subject''
token consists of the same elements as the
``subject''
token, with the addition of type/length and variable size machine address
information in the terminal ID.
An
``expanded subject''
token can be created using
au_to_subject32_ex3
or
au_to_subject64_ex3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Audit ID4 bytesAudit user ID"
"Effective User ID4 bytesEffective user ID"
"Effective Group ID4 bytesEffective group ID"
"Real User ID4 bytesReal user ID"
"Real Group ID4 bytesReal group ID"
"Process ID4 bytesProcess ID"
"Session ID4 bytesAudit session ID"
"Terminal Port ID4/8 bytesTerminal port ID (32/64-bits)"
"Terminal Address Type/Length1 byteLength of machine address"
"Terminal Machine Address4 bytesIPv4 or IPv6 address of machine"
System V IPC Token
The
``System V IPC''
token contains the System V IPC message handle, semaphore handle or shared
memory handle.
A System V IPC token may be created using
+.Xr au_to_ipc 3 .
FieldBytesDescription
"Token ID1 byteToken ID"
"Object ID type1 byteObject ID"
"Object ID4 bytesObject ID"
Text Token
The
``text''
token contains a single NUL-terminated text string.
A
``text''
token may be created using
au_to_text3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Text Length2 bytesLength of text string including NUL"
"TextN bytes + 1 NULText string including NUL"
Attribute Token
The
``attribute''
token describes the attributes of a file associated with the audit event.
As files may be identified by 0, 1, or many path names, a path name is not
included with the attribute block for a file; optional
``path''
tokens may also be present in an audit record indicating which path, if any,
was used to reach the object.
An
``attribute''
token can be created using
au_to_attr323
or
au_to_attr643.
FieldBytesDescription
"Token ID1 byteToken ID"
"File Access Mode1 bytemode_t associated with file"
"Owner User ID4 bytesuid_t associated with file"
"Owner Group ID4 bytesgid_t associated with file"
"File System ID4 bytesfsid_t associated with file"
"File System Node ID8 bytesino_t associated with file"
"Device4/8 bytesDevice major/minor number (32/64-bit)"
Groups Token
The
``groups''
token contains a list of group IDs associated with the audit event.
A
``groups''
token can be created using
au_to_groups3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Number of Groups2 bytesNumber of groups in token"
"Group ListN * 4 bytesList of N group IDs"
System V IPC Permission Token
The
``System V IPC permission''
token contains a System V IPC access permissions.
A System V IPC permission token may be created using
au_to_ipc_perm3.
FieldBytesDescription
"Token ID1 byteToken ID"
Owner user ID Ta 4 bytes Ta User ID of IPC owner
Owner group ID Ta 4 bytes Ta Group ID of IPC owner
Creator user ID Ta 4 bytes Ta User ID of IPC creator
Creator group ID Ta 4 bytes Ta Group ID of IPC creator
Access mode Ta 4 bytes Ta Access mode
Sequnce number Ta 4 bytes Ta Sequnce number
Key Ta 4 bytes Ta IPC key
Arg Token
The
``arg''
token contains informations about arguments of the system call.
Depending on the size of the desired argument value, an Arg token may be
created using
au_to_arg323
or
au_to_arg643.
FieldBytesDescription
"Token ID1 byteToken ID"
Argument ID Ta 1 byte Ta Argument ID
Argument value Ta 4/8 bytes Ta Argument value
Length Ta 2 bytes Ta Length of the text
Text Ta N bytes + 1 nul Ta The string including nul
exec_args Token
The
``exec_args''
token contains informations about arguements of the exec() system call.
An exec_args token may be created using
au_to_exec_args3.
FieldBytesDescription
"Token ID1 byteToken ID"
Count Ta 4 bytes Ta Number of arguments
Text Ta * bytes Ta Count null-terminated strings
exec_env Token
The
``exec_env''
token contains current eviroment variables to an exec() system call.
An exec_args token may be created using
au_to_exec_env3.
FieldBytesDescription
"Token ID1 byteToken ID"
Count ID Ta 4 bytes Ta Number of variables
Text Ta * bytes Ta Count nul-terminated strings
Exit Token
The
``exit''
token contains process exit/return code information.
An
``exit''
token can be created using
au_to_exit3.
FieldBytesDescription
"Token ID1 byteToken ID"
"Status4 bytesProcess status on exit"
"Return Value4 bytesProcess return value on exit"
Socket Token
The
``socket''
token contains informations about UNIX domain and Internet sockets.
Each token has four or eight fields.
Depend on type of socket a socket token may be created using
au_to_sock_unix3,
au_to_sock_inet323or
au_to_sock_inet1283.
Field Ta Bytes Ta Description
Token ID Ta 1 byte Ta Token ID
Socket family Ta 2 bytes Ta Socket family
Local port Ta 2 bytes Ta Local port
Socket address Ta 4 bytes Ta Socket address
FieldBytesDescription
"Token ID1 byteToken ID"
+.It Li "Socket domain" Ta "4 bytes" Ta "Socket domain"
+.It Li "Socket family" Ta "2 bytes" Ta "Socket family"
+.It Li "Address type" Ta "1 byte" Ta "Address type (IPv4/IPv6)"
+.It Li "Local port" Ta "2 bytes" Ta "Local port"
+.It Li "Local IP address" Ta "4/16 bytes" Ta "Local IP address"
+.It Li "Remote port" Ta "2 bytes" Ta "Remote port"
+.It Li "Remote IP address" Ta "4/16 bytes" Ta "Remote IP address"
Expanded Socket Token
The
``expanded socket''
token ...
FieldBytesDescription
"Token ID1 byteToken ID"
XXXXX
Seq Token
The
``seq''
token contains a unique and monotonically increasing audit event sequence ID.
Due to the limited range of 32 bits, serial number arithmetic and caution
should be used when comparing sequence numbers.
The OpenBSM implementation was created by McAfee Research, the security
division of McAfee Inc., under contract to Apple Computer Inc. in 2004.
It was subsequently adopted by the TrustedBSD Project as the foundation for
the OpenBSM distribution.
AUTHORS
The Basic Security Module (BSM) interface to audit records and audit event
stream format were defined by Sun Microsystems.
The
``How to print''
field in the
``arbitrary data''
token has undefined values.
The
``in_addr''
and
``in_addr_ex''
token layout documented here appears to be in conflict with the
libbsm(3)
implementations of
au_to_in_addr3
and
au_to_in_addr_ex3.
